Large deposits of oil shale are found in many locations throughout the world, and extensive efforts have been undertaken to develop oil shale as a source of hydrocarbon products. In fact, the potential reserves of liquid hydrocarbons to be derived from oil shale greatly exceed the known reserves of liquid hydrocarbons to be derived from petroleum. It has long been known that oil may be extracted by heat from various extensive deposits of porous minerals known by their generic term "oil shale", which are permeated by a complex organic material called "kerogen". Upon application of heat, the kerogen is converted to a complex mixture of hydrocarbons and hydrocarbon derivatives which may be recovered from a retort as a liquid shale oil product.
However, many oil shales, particularly the Devonian black shales of the eastern United States, contain large amounts of iron pyrites (FeS.sub.2). For example, a New Albany, Bullett County, oil shale contains about 6 percent pyritic sulfur and 12 percent organic carbon. This pyrite is the cause of at least two serious problems in the winning of oil from the shales. At retorting temperatures, the iron pyrite reacts with the organic matter, generated from kerogen, robbing it of hydrogen, thus resulting in a poorer product and/or a lower yield of oils. Additionally, as a consequence of the foregoing reaction, large quantities of hydrogen sulfide are formed. Because of environmental considerations and due to its corrosive characteristics, the hydrogen sulfide has to be removed, for example, by converting it to sulfur.
Additionally, because of the high temperatures required in known retorts and retorting processes for obtaining hydrocarbon values from oil shale, and the resultant need for large amounts of energy to provide such heat, it is desirable to retort as little oil shale as possible to obtain each gallon of oil.
Thus, it would be advantageous to have a process wherein the oil shale ore is upgraded and wherein at the same time the oil shale is treated to substantially reduce the amount of hydrogen sulfide formed during subsequent retorting.